What I never got is why people are so eager to board the plane as early as possible. My strategy is to wait until everyone is in and to go in last. This way I'm in the airplane as short as possible. I always try to get a seat in the center so that nobody needs to stand up and let me into my seat.
it's the battle for overhead bin space! I never check bags but that means I need space in the overhead bins. Last one on means the space is all full up usually.